The correct option is D Introduction of gene isolated from the bone marrow cells which produce ADA, into the cells of the patient at early embryonic stages
Adenosine deaminase (ADA) deficiency can be treated by bone marrow transplantation, or by enzyme replacement therapy, in which functional ADA is given to the patient by injection. But permanent treatment can be done by introduction of gene isolated from bone marrow cells, which produces ADA, into the cells of the patient at early embryonic stage.